There are three components of the study: technical development to define the imaging protocol; conduct the observational study of blood flow patterns in study subjects; define the anatomy and flow parameters for construction of flow models. The development of the principal imaging protocol is complete; the portal anatomy and flow patterns can be reproducibly imaged. During the period of technical development, we have observed evidence of the phenomenon of blood streaming which is the central hypothesis of our study. The observational study of subjects after fasting and after a meal started July 1999. We have accrued 22 volunteers to date. Preliminary anatomic and flow data has been collected for model construction; a preliminary model has been constructed. The magnetic resonance examinations of the patients enrolled in the pivotal study are completed. Suitable software for data analysis has become available and data analysis is underway.